This application claims the priority of Korean Patent Application No. 2004-28628 filed on Apr. 26, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an image sensor module and a method of fabricating the same, and more particularly, to an image sensor module in which a focal length of a lens can be automatically aligned, and a method of fabricating the same, and a method of automatically controlling a focus of the lens.
2. Description of the Related Art
Due to the recent popularity of various mobile electronic products such as cellular phones, Portable Digital Assistants (PDA), and digital cameras, digital photography has become very important. Specifically, a palm-sized apparatus having a digital camera such as PDA and cellular phone employs a key technique for photographing and transmitting an image. Accordingly, an image sensor module for processing an external image into a digital signal is of importance.
FIG. 1 is a cross-sectional view schematically illustrating a conventional image sensor module.
Referring to FIG. 1, an image sensor chip 12 is mounted on and electrically connected with the substrate 10 by a bonding wire 14. A digital signal processor (DSP) chip 16 can be mounted onto the other surface of the substrate 10 opposite to the image sensor chip 12. The DSP chip 16 is attached to the substrate 10 and electrically thereto to the substrate 10 through the bonding wire 14. After that, the DSP chip 16 is encapsulated by a mold 18. A housing 20 is attached onto the substrate 10 and has an opening 22 for exposing an upper surface of the image sensor chip 12. A lens holder 24 is provided on the housing 20. The lens holder 24 extends the opening 22 vertically and upwardly and has a lens assembly unit 26 affixed to an inner sidewall thereof. The lens assembly unit 26 has a plurality of lenses and is threaded into the lens holder 24.
The lens assembly unit 26 includes a toothed connection unit on an outer side surface thereof for threaded engagement with the toothed connection unit corresponding to an inner sidewall of the lens holder 24. The lens assembly unit 26 is affixed to manually control a vertical distance (d) between an upper surface of the image sensor chip 12 and the lowermost end of a lens 28. That is, the vertical distance (d) is controlled to be consistent with the focal length provided by the plurality of lenses 28. An infrared screen filter 30 can be provided between the lens 28 and the image sensor chip 12 to screen against infrared radiation.
However, a conventional method of fabricating the image sensor module including the lens assembly unit 26 has several drawbacks. First, because the vertical distance (d) is controlled in a screw manner, impurity particles are generated due to the friction between the screw threads of the lens assembly unit 26 and those of the lens holder 24 formed of a polymer material, for example, polycarbonate and polyphenylsulfide. Further, due to the manual alignment control of the lens 28, a separate process is required for manually controlling the focal length. Furthermore, since a diameter or a width (W1) of the lens holder 24 is determined including the lens assembly unit 26, it is disadvantageous when the image sensor module is to be miniaturized.
To solve the above drawbacks, U.S. Pat. No. 6,483,652 discloses an image sensor module in which a predetermined jaw is provided at an inner sidewall of the lens holder 24 without a lens assembly unit 26 to affix a lens. However, since the U.S. patent has the limitation to single-lens optics, it has a difficulty in the application of optics employing a plurality of lenses. In detail, to affix the plurality of lenses, a plurality of jaws are provided at an inner sidewall of the lens holder. However, the plurality of jaws have each a different radius to affix the plurality of lenses to the lens holder 24. Accordingly, the lenses also need to have different radiuses. Therefore, it has been very difficult to control the focal lengths of the lenses. Further, because the lens needs to be inserted into the lens holder one-by-one, the process of inserting the lens is complicated, thereby increasing the manufacturing costs. Also, it has been difficult to employ injection molding since the lens holder should be made very precisely.